This application claims priority from British Patent Application No. 0019598.2 filed on Aug. 9, 2000 and British Patent Application No. 0112605.1 filed on May 23, 2001.
The present invention relates to a locking or latching mechanism, and in particular to a locking or latching mechanism for locking or latching a door to a door frame.
There are many different types of locks and latches known for different purposes. A common lock for locking doors, for example cupboard or cabinet doors, is known as a twist lock. This comprises a striker having an enlarged, flattened head that is receivable within a keep through an opening in the keep. The striker is rotatable between a first position in which the enlarged head is able to pass through the opening of the keep, and a second position in which the enlarged head is unable to pass through the opening in the keep. The striker may be rotated freely, for example by a handle when the mechanism is used merely as a latch, or may require a key to be rotated where the mechanism is to be used as a security lock. With such an arrangement, the striker is turned to a position such that the enlarged head may pass through the opening of the keep when it is desired to unfasten the lock, and to a position in which the enlarged head is unable to pass through the opening of the keep when the lock is to be fastened.
Where such locks are used for cupboard or cabinet doors, it is usual for the striker to be provided on the door, and the keep to be mounted on the door frame. One application for such locks is for refrigerators, especially industrial or commercial refrigerators that may contain goods of considerable value that need to be secured.
A problem with known twist locks is that they require accurate alignment between the striker and the keep. For example, where the lock is provided on a cupboard or cabinet, there is the possibility that some misalignment may occur during use between the striker and the keep. This is especially the case for large cabinets or cupboards where a small movement in the connection between the door and the carcass of the cupboard near the hinge will result in a relatively large movement between the door and carcass at the locking position. As a result of this, there is the risk that, when the door is closed, the striker will not align with and pass into the opening of the keep, but instead will strike the keep itself. This is liable to cause damage to the locking mechanism. Commonly, this will result in the locking barrel being forced from the locking mechanism, causing damage to the locking mechanism.
A further problem occurs where an attempt is made to close the door whilst the striker is in a locked position. For example, where the lock is provided on a cupboard or refrigerator that need frequently to be opened and closed, it is not uncommon for the keys to be left in the lock. In this case, there is a risk that when the door is open, the striker will accidentally be turned to the locked position. When the door is then closed, the striker will hit the keep, not being able to pass through the opening. This is liable to cause damage similar to that caused when the striker and keep become misaligned. A further problem in this case is that the attempt to close the door will be unsuccessful. Especially where the door must be kept closed, for example where the door is the door of a cold storage chamber such as a refrigerator, and if the door is left open this may lead to the temperature in the chamber exceeding an acceptable level, this may present a considerable problem.
However damage occurs to a lock, this will cause inconvenience and expense. If it is not possible to lock the door, there is a security risk. Further, the lock will require repair or replacement.
According to the present invention, a locking or latching mechanism comprises a striker having an enlarged head and a keep, the keep including an opening through which the enlarged head of the striker can pass, in which the mechanism is in a locked or latched condition when the enlarged head of the striker is received by and retained by the keep, the keep being provided loosely within a housing to permit automatic alignment between the striker and the keep when the striker is moved towards and into the keep.
With the mechanism according to the present invention, a greater degree of misalignment between the striker and the keep is permitted, whilst not affecting the operation of the locking or latching mechanism, and without causing damage to the lock or latch. In particular, if there is misalignment between the striker and the keep as the striker is moved into contact with the keep, the keep will have a degree of freedom of movement allowing it to align automatically with the striker.
It is preferred that the keep is formed of a resilient material. In this way, even if the keep is not able to move into perfect alignment with the striker, the resilience of the keep will allow this to deform to allow the opening in the keep to expand to allow the striker to pass through the opening without causing damage to the locking mechanism. In one aspect, the keep may be fixed at certain points, with the looseness being achieved in the region through which the striker passes by the resilience of the keep. Forming an angled entry into the opening of the keep may assist this.
A suitable resilient material from which the keep may be formed is steel.
Where the mechanism is to be used as a latch, the normal opening of the keep should be smaller than the enlarged head of the striker. In this case, when the striker is moved towards the keep, the keep is resiliently deformed to allow the enlarged head to pass into the keep. When the enlarged head has passed into the keep, the keep reverts to its normal configuration, retaining the enlarged head within the keep to latch the mechanism closed. To open the mechanism, it is necessary to apply sufficient force to cause the keep to deform to allow the enlarged head of the striker to pass through the opening of the keep.
Where the mechanism is to operate as a lock, it is preferred that the enlarged head of the striker has a different width than height. In this case, by rotation of the striker about its axis, a different profile may be presented. In particular, the striker may be rotated to a position in which it is in general alignment with the opening of the keep, and in this position will be able freely to pass into and out of the keep. This is the unlocked condition. When the striker is rotated to a position out of alignment with the opening to the keep, the enlarged head will be unable to pass freely out of the keep. This is the locked condition.
The use of a resilient material for the keep, preferably also with an angled entry, helps prevent damage to the locking mechanism in the event that an attempt is made to close the mechanism whilst the striker is in a locked orientation. In this case, the keep will bend to increase the size of the opening, and will allow the striker to pass into the keep. In this case, the lock or latch will be in a locked state, but without causing damage to the mechanism. Also, this will allow the door to close, even if the striker has accidentally been turned to the locked orientation, and therefore will ensure that the door will not remain open. In this case, the door will be closed in the locked condition.
Where the mechanism is used as a lock in this way, it is preferred that the keep includes a shoulder on the inside of the opening, such that the enlarged head contacts this shoulder and prevents opening of the keep to allow the enlarged head to pass though the opening by the application of force. In this way, it is only possible to open the lock by turning the striker to bring this into alignment with the opening, in which alignment the enlarged head is able to pass easily through the opening of the keep.
The housing in which the keep is loosely provided preferably has a large opening corresponding to the opening of the keep at any position in which the keep may move.
In a preferred embodiment, the keep comprises a wire defining an opening through which the head of the striker passes, and which retains the head. This is of advantage as such a keep has minimal depth. In this case, it is preferred that the keep comprises at least two legs that define an opening, and in this case that the legs are formed as the legs of a generally U-shaped wire, or as the extensions of a coil. This allows the loose mounting of the keep. Advantageously, the wire is formed of a resilient material. Since the wire will be deformable in the direction of movement of the striker, it is preferred that at least one support is provided to limit the movement of the keep in the direction of the striker.